Adjustable measuring devices exist, but with one or more drawbacks. U.S. Pat. No. 5,678,450 to Robbins et al. discloses an adjustable measurement container in which the size of the scoop is adjusted by linearly sliding a sliding member that includes a covering portion (unnumbered) and a partition (dam 42). U.S. Pat. No. 6,125,699 to Molenaar discloses an adjustable measuring spoon in which the size of the scoop is adjusted by rotating a pivoting member that also includes a covering portion (gate 23) and a partition (49). Neither patent, however, discloses an intimate, hermetically-sealing relationship between the moving parts or suggests how the devices could be modified to attain that.